When extracting hydrocarbons from production wells drilled into hydrocarbon formations, it is a safety and regulatory requirement that pressurized fluids and/or gases coming from the drilled well (e.g. sour gases), be isolated from surface to thereby prevent their escape to atmosphere at the surface of the well.
Specifically, downhole pump assemblies typically possess seal rings, which when the pump is installed in the operative position, typically engage circumferential seals within the casing or tubing in which the downhole pump assembly was placed and positioned, thereby preventing pressurized fluids and/or gases from flowing to surface except through the pump and thereby through the production tubing.
However, any raising of the downhole pump for the purposes of repair or replacement, as taught in the prior art, necessarily disengages the sealing rings, thereby releasing the downhole pressurized fluids and/or gases to surface.
To avoid this undesirable situation and to avoid communication with surface when a downhole pump assembly is being replaced, the prior art teaches that a well be effectively “killed” prior to pump removal, typically by pumping viscous fluids downhole to temporarily seal the well prior to blowout preventer installation and the pump being removed.
The process of “killing” a well each time to service downhole components is costly and time-consuming. Additionally, in some instances, the “killing” process may be too effective where it becomes difficult, and sometimes impossible, to later “restore” the well by removing the viscous fluids. Therefore, a well that is temporarily killed may unintentionally be permanently killed or unable to be brought back on-stream as effectively as before.
In heavy oil formations, where the produced oil contains large amounts of abrasive sand, wear on the pumps is extensive. This results in the necessity to frequently replace the pumps. As described above, replacing the pumps results in the undesirable need in the prior art to “kill” the well so that pressurized fluids and/or gases deep in the formation are not otherwise allowed to flow directly to surface.
A real need exists for a specialized apparatus and method for removing worn or defective pumps which avoids the need to first “kill” the well, or alternatively is able to avoid the pollution which would otherwise result from the release of pressurized fluids and/or gases from within the formation to surface via the open well.